Question 662803
At least in the USA, a good dose of algebra gets injected into geometry.
That's why you'll keep seeing x here and there.
 
I assume your problem looks like this:
{{{drawing(300,300,-1,11,-1,5,
triangle(0,0,10,0,2.98,4.42),
locate(0.4,0.35,75+x),locate(8.2,0.5,56^o),locate(2.7,4.1,50^o)
)}}} The geometry bit: The measures of the 3 angles of a triangle add up to {{{180^o}}}.
The algebra:
{{{50+56+(75+x)=180}}} --> {{{50+56+75+x=180}}} --> {{{181+x=180}}}
Now we subtract 181 from both sides of the equal sign.
{{{181+x=180}}} --> {{{181+x-181=180-181}}} --> {{{highlight(x=-1)}}}
That {{{x}}} was worth {{{-1^o}}}, which added to {{{75^o}}}, made the third angle measure {{{74^o}}}.
(Strange problem. I did not expect a negative {{{x}}}, but negative numbers are OK with me).